The present invention relates to exercise devices used on the human body and, more particularly, to exercise devices wherein the resistance curve experienced by the human body can be selectively and easily adjusted.
Most exercise devices provide only a single resistance curve that cannot be altered to conform to individual requirements. Recently, a number of exercise devices have been developed that enable resistance curves to be varied. However, those exercise devices suffer from a number of practical and functional limitations. For example, negative forces often result during the range of motion of the exercise device which can lead to less than optimal conditioning and loss of control of the exercise device by the user.
U.S. Pat. No. 5,286,243 discloses an exercise device combining the resistance generated by a plurality of torque arms with a conversion mechanism that creates a greater degree of rotation of the torque arms than that of the exercise arm. It is possible, through proper relative placement of weights along designated torque arms, to achieve desirable resistance curves. However, both positive and negative resistance forces are possible during the exercise motion. Consistently maintaining a desired resistance curve and consistently maintaining a positive resistance load throughout the exercise motion requires proper adjustment of numerous torque arm variables. The proper adjustment of such variables may in many cases be beyond the patience and/or the knowledge of the average exercise equipment user.
U.S. Patent Application Ser. No. 08/609,244, the disclosure of which is incorporated herein by reference, discloses an exercise device in which resistance curves can be selectively varied and controlled to achieve a desired positive resistance curve notwithstanding the degree of rotation of the exercise motion. In that exercise device, a user interface member (or exercise member) is connected to a first shaft such that when the user interface member is displaced by a user the first shaft is caused to rotate. A second shaft is also rotatably supported on a support frame of the device. A torque arm assembly including a plurality of torque arms (for supporting weight members) are connected to the second shaft. A conversion mechanism connects the first and the second shafts to limit the degree of rotation of the second shaft in such a manner that the resistance generated by the torque arm assembly cannot result in a negative resistance force regardless of the loading of the torque arms.
In general, the conversion mechanism of U.S. Patent Application Ser. No. 08/609,244 is a beltwheel assembly. Beltwheel assemblies provide the advantage of effecting a linear or constant conversion of the degree of rotation between the user interface member (or exercise arm) and the torque arm assembly. Thus, the normalized resistance curve or strength curve for each of the torque arms is unaffected by the beltwheel conversion mechanism. Nonetheless, beltwheel conversion mechanisms suffer from a number of significant drawbacks. For example, belt wheel assemblies can be expensive and difficult to manufacture. Moreover, deformation of the belt during use thereof can affect the conversion. Likewise, the belts of beltwheel assemblies are prone to failure/breakage during use, giving rise to the potential for injury to the user.
It is very desirable to develop exercise devices that reduce or eliminate the drawbacks associated with current exercise devices.
The present invention provides an exercise device in which resistance curves can be selectively varied and controlled. The present invention includes a torque arm assembly that preferably comprises a plurality of torque arms or pegs positioned at different radial positions along a radius of rotation of the torque arm assembly such that the relevant placement of weight members on the torque arms results in an endless array of resistance curves. In any such resistance curve, the present invention preferably continuously maintains a positive resistance force regardless of the manner of loading of the torque arms.
In general, the present invention provides an exercise device for generating a plurality of resistance curves including a support frame and a torque arm assembly rotatably connected to the support frame via, for example, a rotating shaft of the torque arm assembly. As described above, the torque arm assembly includes a plurality of torque arms. Each of the plurality of torque arms includes a support member to position a weight member thereon. A user interface member is connected to an exercise arm or shaft. Displacement of the user interface by the use of the exercised device causes the exercise arm to rotate. A conversion mechanism including a linkage assembly operatively connects the exercise arm and the torque arm assembly. The conversion mechanism controls the degree of rotation of the torque arm assembly as a function of the rotation of the exercise arm.
The linkage assembly of the conversion mechanism is preferably adapted to provide a generally optimized desired normalized resistance or torque curve as experience by the user (that is, torque as measured at the exercise arm) for each of the torque arms. In that regard, the nonlinear conversion of the linkage assembly and the sinusoidal variation of each of the torque arms is combined to provide a simultaneously optimized resistance curve for each of the torque arms.
The linkage assembly of the present invention provides a number of advantages over beltwheel assembly conversion mechanisms used in current exercise devices. For example, linkage assemblies are stronger than belt wheel assemblies and do not wear/fail with repeated use over extended periods of time. Moreover, the linkage assemblies of the present invention are relatively simple and inexpensive to manufacture.
A number of currently available exercise devices utilize linkage assemblies to connect an exercise arm to a weight assembly. Unlike such exercise devices, the multiple defined torque curves (as determined by the multiple torque arms of the torque arm assembly) of the present invention, the relatively large conversion ratios of the conversion mechanism of the present invention, and/or the relatively large range of motion of the exercise arm and/or the torque arm greatly complicate the design of the linkage assembly. Indeed, the inherent nonlinearity of linkage assemblies can substantially and undesirably alter the sinusoidal resistance curves (that is, the torque on the exercise arm) resulting from a rotating torque arm assembly. In that regard, the resistance and the rate of change of that resistance experienced by the user over the range of motion of the exercise arm is a sum of the effects of the sinusoidal torque resulting from rotation of the torque arm assembly and the nonlinear conversion of the sinusoidal torque by the linkage assembly. Because of their inherent nonlinearity, linkage assemblies have typically been used in exercise devices in cases wherein (i) there is an approximately 1:1 correspondence between the range of motion of the exercise arm and the torque arm assembly (a conversion ratio of 1.0); (ii) the range of motion of the exercise arm and/or the torque arm assembly is relatively limited (generally, less than approximately 50 degrees); (iii) and/or the torque arm assembly can be loaded at only a single position.
In that regard, matching a single load curve to a single load force curve using a linkage assembly as done in a number of other exercise devices is relatively simple. For example, if the nonlinearity of a linkage assembly in such an exercise device is such that the user interface arm and the load or torque arm assembly are rotating in the correct angle, but the force curve is incorrect, the designer can simply rotate the weight loading point (for example, a torque arm or weight peg) to a different angle on the arc of rotation of the torque arm assembly to match the load curve to the linkage curve and give the desired resistance curve. In the case that the torque arm assembly has multiple loading positions as in the exercise device of the present invention, however, one cannot merely/solely rotate such multiple loading points along the arc of rotation of the torque arm assembly to provide the desired force curve for each of the multiple loading points (particularly if negative torques/forces are to be avoided). Simply, relocating the weight points or pegs to different positions on the rotation of the torque arm assembly (as done in current, single-loading-point linkage assembly systems) results in resistance curves that do not match the desired resistance curves (for example, the resistance curves that would result in a linear conversion for given positions of the torque arms) because of the limited space and/or the nonlinear physics of the conversion mechanism. In the case of three loading positions, for example, one has three variable positions and three desired/ideal force curves. Furthermore, the rate of change in the force and/or the direction of that change (that is, a positive or a negative change) are different for each force curve as determined by the position/angle of the torque arm on the sinusoidal curve. Prior to the present invention, combining such multiple nonlinear, sinusoidal torque changes with the nonlinear conversion of a linkage mechanism to achieve a desirable resistance curve for each torque arm was not attempted for the conversion ratios and ranges of motion of the present invention.
Moreover, the greater the degree of conversion between the range of motion of the exercise arm and the range of motion of the torque arm assembly(that is, the more the conversion ratio varies from 1), the greater the nonlinearity that arises from a linkage assembly. Likewise, the greater the range of motion of the exercise arm assembly and/or the torque arm assembly, the greater the nonlinearity that arises from a linkage assembly. Generally, in the case that the conversion ratio is approximately 1 and/or the range of motion of the exercise arm assembly and the torque arm assembly are less than approximately 50 degrees, the nonlinearity of the conversion can be ignored even in the case of a torque arm assembly having multiple loading points.
As used herein, the term xe2x80x9cconversion ratioxe2x80x9d refers generally to the range of motion (in degrees) of the exercise arm divided by the range of motion (in degrees) of the torque arm assembly. Thus, in an exercise device in which the exercise arm assembly rotates 140 degrees and the torque arm assembly rotates 70 degrees, the conversion ratio is 2.0. In an exercise device in which the exercise arm assembly rotates 70 degrees and the torque arm assembly rotates 140 degrees, the conversion ratio is 0.5.
The present inventor has surprisingly discovered that it is possible adapt a linkage assembly to provide a desired resistance curve for each of a plurality of torque arms on a rotating torque arm assembly, while preventing negative resistance for any loading of the torque arms. The present inventor has discovered that such multiple desirable resistance curves can be achieved even if (i) the conversion ratio significantly deviates from 1, and/or (ii) the range of motion of the exercise arm assembly and/or the torque arm assembly is greater than approximately 50 degrees.
In one aspect the present invention provides an exercise device for generating a plurality of resistance curves including: a support frame, a first shaft rotatably supported on the support frame; a user interface member connected to the first shaft which, when displaced by a user, causes the first shaft to rotate more than 90 degrees and a second shaft rotatably supported on the support frame. A linkage mechanism (inherently causing a variable resistance force over the range of motion thereof) connects the first shaft and the second shaft, thereby controlling the relative rates (and degrees) of rotation of the first and second shafts.
The exercise device also includes a torque arm assembly having an upper torque arm and a lower torque arm connected to the second shaft at different predetermined angular positions. Each torque arm includes at least one weight support member thereon.
The relative positions of the connections within the linkage mechanism are coordinated with the relative angular positions of each torque arm such that when the user interface member is displaced by the user and a weight member is placed on the upper torque arm, the aggregate effect of the linkage mechanism and upper torque arm causes: (i) a maximum torque to be applied to the first shaft at some point during the first 45 degrees of rotation of the first shaft; and (ii) a minimum torque to be applied to the first shaft at some point during the last 45 degrees of rotation of the first shaft. Likewise, the relative positions of the connections within the linkage mechanism are coordinated with the relative angular positions of each torque arm such that when the user interface member is displaced by the user and a weight member is placed on the lower torque arm, the aggregate effect of the linkage mechanism and lower torque arm causes: (i) a maximum torque to be applied to the first shaft at some point during the last 45 degrees of rotation of the first shaft; and (ii) a minimum torque to be applied to the first shaft at some point during the first 45 degrees of rotation of the first shaft.
Preferably, the resistance generated by the linkage mechanism and torque arm assembly does not and, indeed cannot, result in a negative resistance force at any point during the rotation of the first shaft.
In another embodiment, the exercise device includes another torque arm at an angular position intermediate to the upper torque arm and the lower torque arm. Multiple intermediate torque arms can be provided. The relative positions of the connections within the linkage mechanism are coordinated with the relative angular position of the intermediate torque arm such that when the user interface member is displaced by the user and a weight member is placed on the intermediate torque arm, the aggregate effect of the linkage mechanism and intermediate torque arm causes a maximum torque to be applied to the first shaft at some point during the middle 45 degrees of rotation of the first shaft.
In one aspect of the present invention, the linkage assembly of the conversion mechanism of the present invention is preferably adapted or adjusted to reduce or to optimize the effect thereof on a normalized torque curve resulting for each of several torque arms positioned at different angular positions. As used herein, the phrase xe2x80x9cnormalized torque curvexe2x80x9d refers generally to the percent of maximum resistance experienced at the various points along the range of motion of a torque arm. In other words, in this aspect of the present invention, the nonlinearity of the conversion of the linkage assembly is preferably reduced or optimized over the range of motion of the exercise arm for the torque arms. The position of each of the torque arms can also be altered to further alter the corresponding resistance curves to arrive at a desire result.
Surprisingly, the above results can be accomplished even if the conversion ration is greater than approximately 1.25. The conversion ratio can even be greater than approximately 1.5. Indeed, the conversion ratio can even be greater than approximately 1.75 Furthermore, the results can be accomplished even in the case that the range of motion of either the exercise arm or the torque arm is greater than 50 degrees. Indeed, the results can be accomplished even in the highly desirable case that the range of motion of the exercise arm is greater than 90 degrees.
In the present invention, the multiple uniquely defined strength/torque curves of the torque arm assembly are preferably matched to or combined with the linkage assembly curve to provide a desired composite resistance curves by mapping the points of rotation of the links of the linkage assembly into two dimensional space and studying the resistance/torque experienced by the user (at the exercise arm) at incremental positions along the range of motion of the exercise arm for each of a plurality of torque arms positioned at different angular orientation for each set of such points. In that regard, the method preferably further includes the steps of: changing the location of at least one of the points of rotation in two-dimensional space to create at least a second set of point; and studying the force curve experienced by the exercise arm at incremental positions along the range of motion of the exercise arm for the second set of points. These steps are preferably repeated to reduce the effect of the linkage assembly on the sinusoidal resistance curves experienced at the exercise arm. The present inventor has discovered that the linkage assemblies of the present invention can be relatively quickly designed/optimized by studying the effect of moving the position or such points or rotation in two-dimensional space (the third, dimension can generally be ignored for the purposes of this study). Preferably, one of the points of rotation (for example, the point about which the torque arm assembly rotates) is preferably used as reference point or origin in the two-dimensional space. Once the position of each of the points of rotation is determined/optimized, this result provides the relative positions and lengths/structure of the links required. The results of this optimization can be scaled to larger dimensions than those used in the study. Moreover, the angular position of one or more of the torque arms can also be changed to provide the desired resistance curve.
Other details, objects and advantages of the present invention will become apparent as the following detailed description of preferred embodiments of practicing the invention proceeds.